JP2000340670A - Insulating film and formation thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate dry etching by forming an insulating film on the surface of a semiconductor layer and providing the insulating film with a first region and a second region composed of a substance having a dielectric constant different from that of a substance composing the first region. SOLUTION: A insulating film 26 having first and second regions 22, 23 is formed on the surface of a semiconductor layer 20. The first region 22 is formed of SiO2 and the second region 23 is formed of SiOxNy/SiO2. In other words, the second region 23 is composed of a substance having a dielectric constant higher than that of the first region 22. An insulating film 26 composed of the first region 22 functions as a gate insulating film for a transistor element constituting a memory whereas an insulating film 26 composed of the second region 23 functions as a gate insulating film for a transistor element constituting a logic circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulating film and a method for forming the same, and more particularly, to an insulating film having different effective thicknesses.
The present invention relates to an insulating film having two regions and a method for forming the same.

[0002]

2. Description of the Related Art In recent MOS type semiconductor devices,
For example, a memory (DRAM) called a system LSI
A technology for mixing a logic circuit (ASIC) and a logic circuit (ASIC) in the same chip has been developed. In manufacturing a system LSI, generally, a thick insulating film is formed on a memory (DR).
AM) as a gate insulating film for a transistor element, and a thin insulating film as a logic circuit (A
It is necessary to use as a gate insulating film for a transistor element constituting SIC). A conventional method for forming such two types of insulating films having different thicknesses, that is, insulating films having physically different thicknesses, will be described below with reference to FIGS.

[Step-10] First, a first thermal oxidation process is performed on the silicon semiconductor substrate 100 on which the element isolation region 101 and the well region (not shown) are formed by using a known method. A first silicon oxide film 102 is formed on the surface of a silicon semiconductor substrate 100 (see FIG.
1) and (A-2)).

[Step-20] Thereafter, based on the lithography technique, a region where a memory circuit is to be formed is masked with a mask material 1.
03 (see (B-1) and (B-2) in FIG. 6), and the first silicon oxide film 102 in a region where a logic circuit is to be formed is removed based on a dry etching technique.
The surface of the silicon semiconductor substrate 100 is exposed.

[Step-30] Next, the mask material 103 is removed by a known cleaning technique (see (A-1) and (A-2) in FIG. 7), etching residues, etching reaction products, particles, etc. Then, a second thermal oxidation process is performed to form a second silicon oxide film 104 in a region of the silicon semiconductor substrate 100 where a logic circuit is to be formed ((B-1) of FIG. 7 and FIG. (Refer to (B-2)).

[0006]

By the way, in such a conventional method, in [Step-20], the first silicon oxide film 102 in a region where a logic circuit is to be formed is removed based on a dry etching technique. . Therefore, from the viewpoint of the manufacturing process, there is a problem that etching damage and metal contamination occur in a region of the silicon semiconductor substrate 100 where a logic circuit is to be formed. Further, from the viewpoint of device characteristics, it is necessary to perform the thermal oxidation process twice, so that there is a problem that the control of the impurity profile for adjusting the threshold becomes complicated.

Accordingly, an object of the present invention is to provide an insulating film composed of two regions having different effective thicknesses which can be formed without performing dry etching and without performing a plurality of thermal oxidation treatments, and Another object of the present invention is to provide a method for forming such an insulating film.

[0008]

According to the present invention, there is provided an insulating film formed on a surface of a semiconductor layer for achieving the above object.
(A) a first region, and a second region constructed from (B) a substance having a dielectric constant epsilon ₁ different dielectric constant epsilon ₂ with the material constituting the first region It is characterized by the following.

In order to achieve the above object, a method of forming an insulating film according to the present invention has a first region and a second region formed on a surface of a semiconductor layer, and the second region has a first region. Relative permittivity ε ₂ different from the relative permittivity ε _{1 of} the material constituting the region of
A method for forming an insulating film composed of a material having the following characteristics: (a) forming a first region and a second region by oxidizing a surface of a semiconductor layer; Forming a second region formation scheduled region; (b) covering the first region with a mask material;
After performing the nitriding treatment on the exposed second region formation scheduled region,
Removing the mask material. In the step (a), the first region and the second region to be formed by oxidizing the surface of the semiconductor layer may be collectively referred to as an oxide film for convenience.

[0010] In the insulating film or the method of forming the same according to the present invention, the material forming the first region is silicon oxide (S).
iO ₂ ), and the substance constituting the second region can be silicon oxide containing a nitrogen atom. The second region depends on the conditions for forming the second region.
_It consists of _{X NY} , or consists of SiO _{X NY} / SiO ₂ , or it consists of SiO _{X NY} / SiO ₂ / SiO _{X NY} . Here, the material described before "/" occupies the upper layer side of the second region. Also, the boundary between SiO ₂ and SiO _X N _Y is generally not clear. In some cases, the first
May be composed of SiO ₂ / SiO _X N _{Y. In} this case, the concentration of the nitrogen atoms contained in the first region and the concentration of the nitrogen atoms contained in the second region are different. different. In the insulating film of the present invention, the second region preferably has substantially the same thickness as the first region.
Here, “substantially the same thickness” means that the thickness of the second region and the thickness of the first region when it is assumed that nitrogen atoms are removed from the material forming the second region are equal to each other. Means equal. More specifically, when the first region and the second region forming region where the second region is to be formed are formed on the surface of the semiconductor layer, the thickness of the first region and the second region forming It means that the thicknesses of the regions are equal.

In the method for forming an insulating film according to the present invention, dry oxygen gas and water vapor can be used as oxidizing species for oxidizing the surface of the semiconductor layer. As a method for generating water vapor, a method of burning oxygen gas and hydrogen gas (pyrogenic method), a method of heating pure water, a method of bubbling heated pure water with an oxygen gas or an inert gas, a catalyst (for example, NiO Ni-based catalysts such as Pt and Pt
Pt-based catalysts such as O ₂ , Pd-based catalysts such as Pd and PdO, I
r-based catalysts, Ru-based catalysts such as Ru and RuO ₂ , Ag and Ag ₂
Hydrogen gas and oxidizing gas based on a catalytic action using an Ag-based catalyst such as O, an Au-based catalyst, a Cu-based catalyst such as CuO, a Mn-based catalyst such as MnO ₂ , a Co-based catalyst such as Co ₃ O ₄ ). Is reacted. Alternatively,
Electromagnetic waves (for example, frequency 1 GHz) are applied to hydrogen gas and oxygen gas.
Irradiation with a microwave of from about 100 GHz to about 100 GHz to generate water vapor and oxidize the surface of the semiconductor layer using the water vapor (hereinafter referred to as a plasma oxidation method for convenience). When the plasma oxidation method is employed, the first region can be formed on the surface of the semiconductor layer and the second region can be formed by one device, and the configuration of the device can be simplified. be able to. When the plasma oxidation method is employed, the water vapor generated by irradiating the hydrogen gas and the oxygen gas with electromagnetic waves is diluted with an inert gas such as nitrogen, argon, helium, neon, krypton, or xenon, or Using the inert gas as a carrier gas, the first region and the second region may be formed on the surface of the semiconductor layer. Note that an oxide film can also be formed by a method using these methods for generating steam in combination. A method for forming an oxide film on the surface of the semiconductor layer based on the method for generating water vapor may be collectively referred to as a humidification oxidation method.

In the insulating film of the present invention, the second region is preferably formed by nitriding silicon oxide. Further, in the insulating film of the present invention, the second region may be formed by a thermal nitridation method in which the semiconductor layer is heated to a predetermined temperature and is exposed to a nitrogen-based gas. Irradiation is performed to form the second region. In the method of forming an insulating film according to the present invention, the nitridation process in step (c) may be a thermal nitridation process. Is preferably performed because nitrogen treatment can be performed at room temperature, for example.
Note that a method of irradiating the silicon oxide or the region where the second region is to be formed with nitrogen plasma is called a plasma nitriding method.

The nitrogen plasma is composed of excited nitrogen molecules, nitrogen molecule ions, nitrogen atoms or nitrogen atom ions, and these can be generated by irradiating a nitrogen-based gas with electromagnetic waves. Here, examples of the nitrogen-based gas to be irradiated with the electromagnetic wave include a nitrogen gas (N ₂ gas) and a gas that is a compound of a nitrogen atom and an oxygen atom, such as NO, N ₂ O, and NO ₂ . That is, the nitrogen-based gas can be at least one gas selected from the group consisting of N ₂ , NO, N ₂ O, and NO ₂ . The nitrogen-based gas may be a mixture of at least two of these gases. 1 GHz to 10 GHz as electromagnetic waves
A microwave of 0 GHz, for example, a microwave of a frequency of 2.45 GHz can be used.

In the method of forming an insulating film according to the present invention, after the step (c) is completed, N ₂ gas, NO gas, N ₂ O gas or N
Thermal insulating treatment using H ₃ gas may be performed on the insulating film.

In the case of employing the plasma nitriding method, the mask material may be composed of an ordinary resist material, and a combination of an ashing process using oxygen plasma and a subsequent chemical cleaning, for example, a mixed solution of sulfuric acid and hydrogen peroxide is used. The mask material can be removed by the used chemical cleaning.

In the case of manufacturing a MOS type semiconductor device based on a silicon semiconductor substrate, conventionally, before forming an insulating film, the substrate is washed with an NH ₄ OH / H ₂ O ₂ aqueous solution and further washed with HCl / H _2.
The surface of the silicon semiconductor substrate is cleaned by RCA cleaning by cleaning with an O ₂ aqueous solution to remove fine particles and metal impurities from the surface. By the way, when the RCA cleaning is performed, the surface of the silicon semiconductor substrate reacts with the cleaning liquid and has a thickness of 0.5 μm.
A silicon oxide film of about 1 nm is formed. The thickness of such a silicon oxide film is not uniform, and a cleaning solution component remains in the silicon oxide film. Therefore, the silicon semiconductor substrate is immersed in a hydrofluoric acid aqueous solution to remove the silicon oxide film, and further, the chemical component is removed with pure water. Thereby, it is possible to obtain a surface of the silicon semiconductor substrate that is mostly terminated with hydrogen and extremely partially terminated with fluorine. In this specification, obtaining a surface of a silicon semiconductor substrate that is mostly terminated with hydrogen and a very small portion is terminated with fluorine is referred to as exposing the surface of the silicon semiconductor substrate in this specification. I do. afterwards,
An oxide film is formed on the surface of the silicon semiconductor substrate.

By the way, if the atmosphere before forming an oxide film based on the humidifying oxidation method is a high-temperature nitrogen gas atmosphere, the surface of the silicon semiconductor substrate may be roughened (irregularities). Such a phenomenon occurs because a part of the Si—H bond or a part of the Si—F bond formed on the surface of the silicon semiconductor substrate by washing with the hydrofluoric acid aqueous solution and pure water increases hydrogen or fluorine. It is thought to be lost due to thermal desorption and caused by an etching phenomenon occurring on the surface of the silicon semiconductor substrate. For example, when the temperature of a silicon semiconductor substrate is raised to 600 ° C. or more in an argon gas, severe irregularities may be generated on the surface of the silicon semiconductor substrate. The publication of Baifukan, Tadahiro Ohmi, “Ultra Clean ULSI Technology”,
It is described on page 21.

In the method of forming an insulating film according to the present invention, in the step (a), the semiconductor layer is maintained at a temperature at which atoms mainly constituting the semiconductor layer do not desorb from the surface of the semiconductor layer. By starting formation of an oxide film on the surface of the semiconductor layer by the humidifying oxidation method, it is possible to avoid such a phenomenon that the surface of the semiconductor layer is roughened (irregular). The temperature at which atoms mainly constituting the semiconductor layer do not desorb from the surface of the semiconductor layer is a temperature at which bonds between atoms terminating the surface of the semiconductor layer and atoms mainly constituting the semiconductor layer are not broken. Is desirable. When the atoms mainly constituting the semiconductor layer are Si, that is, when the semiconductor layer is composed of a silicon semiconductor substrate, a single crystal silicon layer, a polysilicon layer, or an amorphous silicon layer, the semiconductor layer is removed from the surface of the semiconductor layer. The temperature at which the main constituent atoms do not desorb is the temperature at which the Si-H bond on the surface of the semiconductor layer is not broken, or the temperature at which the Si-F
Desirably, the temperature is such that the bond is not broken. When a silicon semiconductor substrate having a plane orientation of (100) is used as a semiconductor layer, most of hydrogen atoms on the surface of the silicon semiconductor substrate are bonded one by one to two bonds of silicon atoms. It has a -H termination structure.
However, a portion where the surface state of the silicon semiconductor substrate is broken (for example, a step formation portion) has a terminal structure in which a hydrogen atom is bonded to only one bond of a silicon atom, or a three-bonded silicon atom. There is a terminal structure in which a hydrogen atom is bonded to each of the hands. Usually,
The remaining bonds of silicon atoms are bonded to silicon atoms inside the crystal. The expression “Si—H bond” in this specification refers to a terminal structure in which a hydrogen atom is bonded to each of two silicon atoms, and a hydrogen atom is bonded to only one silicon atom. The terminating structure in a state in which a hydrogen atom is bonded to each of the three bonding atoms of a silicon atom, or the terminating structure in a state where a hydrogen atom is bonded to each of three bonding hands of a silicon atom is included. The temperature at which the formation of the oxide film on the surface of the semiconductor layer is started is more specifically a temperature at which water vapor does not condense on the semiconductor layer, preferably 200 ° C. or higher, more preferably 300 ° C. or higher. This is desirable in terms of throughput.

In the step (a), the temperature of the semiconductor layer when the formation of the oxide film is completed by the humidifying oxidation method is
The temperature may be higher than the temperature of the semiconductor layer when starting the formation of the oxide film. In this case, the temperature of the semiconductor layer when the formation of the oxide film is completed is preferably 600 to 1200 ° C., preferably 700 to 1000 ° C., and more preferably 750 to 900 ° C. It is not limited to a value. The temperature may be raised stepwise (stepwise) or continuously.

When the temperature is raised stepwise, after forming an oxide film on the surface of the semiconductor layer by a humidifying oxidation method at a temperature at which atoms mainly constituting the semiconductor layer do not desorb from the surface of the semiconductor layer. A first oxide film forming step of forming an oxide film while holding the semiconductor layer within a temperature range in which atoms mainly constituting the semiconductor layer do not desorb from the surface of the semiconductor layer for a predetermined period; It is preferable to include a second oxide film forming step of further forming an oxide film by a humidifying oxidation method at a temperature higher than a temperature range in which atoms mainly constituting the semiconductor layer do not desorb, until a desired thickness is obtained. . The formation temperature of the oxide film in the second oxide film formation step is 600 to 1200 ° C.
Preferably 700-1000 ° C., more preferably 7
It is desirable that the temperature be 50 to 900 ° C. The upper limit of the semiconductor layer holding temperature range in the first oxide film forming step may be 500 ° C., preferably 450 ° C., and more preferably 400 ° C. The final thickness of the oxide film after the second oxide film forming step may be, for example, a predetermined thickness required for the first region. On the other hand, the thickness of the oxide film after the first oxide film forming step is:
It is preferable to be as thin as possible. However, the plane orientation of the silicon semiconductor substrate currently used in the manufacture of semiconductor devices is almost (100), and no matter how the surface of the silicon semiconductor substrate is smoothed, the surface of the silicon semiconductor substrate must be (100). A step called a step is formed. This step is usually for one layer of silicon atoms, but in some cases, a step for two to three layers may be formed. Therefore,
When a (100) silicon semiconductor substrate is used as the semiconductor layer, the thickness of the oxide film after the first oxide film forming step is preferably 1 nm or more, but is not limited thereto.

A temperature raising step may be included between the first oxide film forming step and the second oxide film forming step. In this case, it is desirable that the atmosphere in the temperature raising step be an inert gas atmosphere or a reduced pressure atmosphere, or an oxidizing atmosphere containing water vapor. Here, examples of the inert gas include a nitrogen gas, an argon gas, and a helium gas. Incidentally, the inert gas or the gas containing water vapor in the atmosphere in the temperature raising step may contain a halogen element. Thereby, the characteristics of the oxide film formed in the first oxide film forming step can be further improved. That is, when the atoms mainly constituting the semiconductor layer are Si, silicon dangling bonds (Si.) And SiOH, which are defects that can be generated in the first oxide film forming step, react with the halogen element in the temperature increasing step and silicon As a result of termination of dangling bonds or dehydration reaction,
These defects, which are reliability deterioration factors, are eliminated. In particular, eliminating these defects is effective for the initial oxide film formed in the first oxide film forming step. Examples of the halogen element include chlorine, bromine, and fluorine, and among them, chlorine is preferable. Examples of the form of the halogen element contained in the inert gas or the gas containing water vapor include hydrogen chloride (HCl), C
Cl ₄ , C ₂ HCl ₃ , Cl ₂ , HBr and NF ₃ can be mentioned. The content of the halogen element in the gas containing an inert gas or water vapor is 0.001 to 10% by volume, preferably 0.001% by volume, based on the form of the molecule or the compound.
5 to 10% by volume, more preferably 0.02 to 10% by volume
It is. For example, when hydrogen chloride gas is used, the content of hydrogen chloride gas in an inert gas or a gas containing water vapor is preferably 0.02 to 10% by volume. Note that the atmosphere in the temperature raising step may be an atmosphere containing steam diluted with an inert gas.

In the method of forming an insulating film according to the present invention, a halogen element may be contained in an oxidizing atmosphere containing water vapor during formation of the oxide film. Thus, an insulating film having excellent time-zero dielectric breakdown (TZDB) characteristics and temporal dielectric breakdown (TDDB) characteristics can be obtained. In addition, as the halogen element, chlorine, bromine and fluorine can be mentioned, and among them, chlorine is preferable. Examples of the form of the halogen element contained in the gas containing water vapor include hydrogen chloride (HCl), CCl ₄ , C ₂ HCl ₃ , and C _2.
l _2, HBr, mention may be made of the NF _3. The content of the halogen element in the gas containing water vapor is 0.001 to 10% by volume, preferably 0.005 to 10% by volume, more preferably 0.02 to 10% by volume, based on the form of the molecule or the compound.
10% by volume. For example, when using hydrogen chloride gas,
The hydrogen chloride gas content in the gas containing water vapor is 0.02 to
Desirably, it is 10% by volume.

In order to further improve the characteristics of the formed oxide film, in the method of forming an insulating film of the present invention, the formed oxide film may be subjected to a heat treatment subsequent to the step (a).

In this case, it is desirable that the atmosphere of the heat treatment be an inert gas atmosphere containing a halogen element.
By heat-treating the oxide film in an inert gas atmosphere containing a halogen element, time-zero dielectric breakdown (TZD)
B) An insulating film having excellent characteristics and time-dependent dielectric breakdown (TDDB) characteristics can be obtained. Examples of the inert gas in the heat treatment include a nitrogen gas, an argon gas, and a helium gas. Also, as a halogen element, chlorine,
Bromine and fluorine can be mentioned, and among them, chlorine is desirable. Examples of the form of the halogen element contained in the inert gas include hydrogen chloride (HCl),
Examples include CCl ₄ , C ₂ HCl ₃ , Cl ₂ , HBr, and NF ₃ . The content of the halogen element in the inert gas ranges from 0.001 to 0.001 based on the form of the molecule or compound.
It is 10% by volume, preferably 0.005 to 10% by volume, and more preferably 0.02 to 10% by volume. For example, when using hydrogen chloride gas, the content of hydrogen chloride gas in the inert gas is preferably 0.02 to 10% by volume.

The formation of the oxide film and the heat treatment can be performed in the same processing chamber. The heat treatment temperature is 700-12
00 ° C, preferably 700 to 1000 ° C, more preferably 700 to 950 ° C. Further, the time of the heat treatment is preferably 1 to 10 minutes when performing the single-wafer processing, and 5 to 60 minutes, preferably 10 to 40 minutes, more preferably 20 to 30 when performing the batch processing. Minutes.

In the case of performing the heat treatment, it is preferable that the temperature of the atmosphere when the formed oxide film is subjected to the heat treatment be higher than the temperature when the formation of the oxide film is completed. in this case,
After the formation of the oxide film is completed, the atmosphere in the processing chamber is switched to an inert gas atmosphere, and then the temperature may be increased to an ambient temperature for performing heat treatment, or the atmosphere may be an inert gas atmosphere containing a halogen element. Then, the temperature may be raised to the ambient temperature for performing the heat treatment. Here, examples of the inert gas include a nitrogen gas, an argon gas, and a helium gas. Examples of the halogen element include chlorine, bromine, and fluorine, and among them, chlorine is preferable. As the form of the halogen element contained in the inert gas, for example, hydrogen chloride (HC
1), CCl ₄ , C ₂ HCl ₃ , Cl ₂ , HBr and NF ₃ . The content of the halogen element in the inert gas is 0.00
1 to 10% by volume, preferably 0.005 to 10% by volume,
More preferably, the content is 0.02 to 10% by volume. For example, when using hydrogen chloride gas, the content of hydrogen chloride gas in the inert gas is preferably 0.02 to 10% by volume.

Usually, an oxide film is formed on the surface of the silicon semiconductor substrate.
Before forming NH_FourOH / H_TwoO _TwoWash with aqueous solution
HCl / H_TwoO_TwoFor RCA cleaning using aqueous solution
Cleaning the surface of the silicon semiconductor substrate
After removing fine particles and metal impurities, an aqueous solution of hydrofluoric acid
Then, the silicon semiconductor substrate is cleaned with pure water. Toko
After that, the silicon semiconductor substrate is exposed to the atmosphere
When the surface of the silicon semiconductor substrate is contaminated, moisture and organic
Objects adhere to the surface of the silicon semiconductor substrate, or
Si atoms on the surface of the silicon semiconductor substrate are converted into hydroxyl groups (OH).
(See, for example, the document "Highly-reliable Ga"
te Oxide Formation for Giga-Scale LSIsby using Clo
sed Wet Cleaning System and Wet Oxidation with Ult
ra-Dry Unloading ", J. Yugami, et al., International
l Electron Device Meeting Technical Digest 95, pp
855-858). In such a case, the acid
When the formation of the oxide film starts, moisture and water are contained in the formed oxide film.
Organic matter or, for example, Si-OH is taken in,
Deterioration of the characteristics of the formed oxide film or generation of defective parts
Can cause. In addition, the defective part is a silicon dangling.
Defects such as bonding bonds (Si.) And Si-H bonds.
Oxide film part or Si-O-Si bond
Is compressed by stress or of Si-O-Si bond
Si- in thick or bulk silicon oxide film
Si-O-Si bond that differs from the angle of the O-Si bond
Means the portion of the oxide film that includes the oxide. Hence this
In order to avoid the occurrence of such problems,
In the formation method, the surface of the semiconductor layer is formed before forming the oxide film.
Exposing the semiconductor layer after surface cleaning to the atmosphere.
Without (ie, for example, cleaning of the semiconductor layer surface from acid
Atmosphere before the start of the oxide film formation process
Or a vacuum atmosphere) to form an oxide film.
Is preferred. As a result, for example, a silicon
When using semiconductor substrates, most are terminated with hydrogen.
Silicon with a surface partially terminated with fluorine
An oxide film can be formed on the surface of a semiconductor substrate.
Prevents reduced oxide film characteristics or defective parts
can do.

When a plasma oxidation method is employed for forming an oxide film, hydrogen gas and oxygen gas are introduced into a processing chamber of a plasma processing apparatus. At this time, the hydrogen gas flows into the processing chamber and flows out of the system. Therefore, it is desirable to introduce oxygen gas before introducing hydrogen gas into the processing chamber in order to prevent a detonation reaction from occurring. Anyway,
There is a possibility that a dry oxide film is formed in the semiconductor layer by introducing oxygen gas into the treatment chamber. Such a dry oxide film has inferior characteristics to an oxide film formed by a humidification oxidation method. Therefore, in order to reliably prevent the formation of a dry oxide film, for example, before starting the formation of an oxide film, a hydrogen gas diluted with an inert gas such as a nitrogen gas is first introduced into the processing chamber, Oxygen gas may be introduced into the vessel. However, in this case, in order to surely prevent the occurrence of a detonation reaction, the concentration of the hydrogen gas should be set so that the hydrogen gas does not react with the oxygen gas and burn, specifically, in air. Below the detonation range (when expressed in volume% with air, 1
8.3% by volume or less), preferably below the flammable range in air (less than 4.0% by volume when expressed in terms of% by volume with air), or alternatively, below the detonation range in oxygen (with oxygen and , The concentration is 15.0% by volume or less, preferably less than the combustion range in oxygen (4.5% by volume or less with oxygen). It is desirable.

As the semiconductor layer, not only a silicon semiconductor substrate such as a silicon single crystal wafer, but also an epitaxial silicon layer, a polysilicon layer, or an amorphous silicon layer on a semiconductor substrate, and further, a silicon semiconductor substrate or a semiconductor element may be formed on these layers. Means an underlayer on which an insulating film is to be formed. Forming an insulating film on a semiconductor layer includes not only forming an insulating film on a semiconductor layer formed on or above a semiconductor substrate or the like, but also forming an insulating film on the surface of a semiconductor substrate. Incidentally, the silicon single crystal wafer can be obtained by the CZ method, the MCZ method, the DLCZ method,
The wafer may be manufactured by any method such as the Z method, or may be subjected to hydrogen annealing in advance. Further, the semiconductor layer may be made of Si-Ge.

When a nitrogen (N ₂ ) gas is used as the nitrogen-based gas, the nitrogen (N ₂ ) is excited in the microwave plasma by the following formula, for example. That is, electrons existing in the plasma are excited, and the excited nitrogen molecules and nitrogen molecule ions are generated by the inelastic collision of the electrons with the nitrogen molecules. These excited nitrogen molecules and nitrogen molecule ions bond oxygen atoms with atoms mainly constituting the semiconductor layer on the surface of the oxide film (for example, when the atoms mainly constituting the semiconductor layer are Si, Si—O Bond) to form a nitrided oxide (e.g., a Si-ON bond),
The surface of the region to be formed is nitrided. The composition of the surface of the region where the second region is to be formed is represented by SiO _X N _Y when the atoms mainly constituting the semiconductor layer are Si.

N ₂ (X ¹ Σg) + e → N ₂ (A ³ Σu ⁺ ) + e Formula (1-1) N ₂ (N ¹ Σg) + e → N ₂ (C ³ Πu) + e Formula ( 1-2) N ₂ (C ³ Πu) + e → N ₂ (B ³ Πg) + hv formula (1-3) N ₂ (B ³ Πg) + e → N ₂ (A ³ Σu ⁺ ) + hv formula (1-4)

In the case where the plasma oxidation method is employed, in an oxygen plasma generated by microwave discharge, the ground state O ₂ (X ³ Σg ⁻ ) is excited by electrons and the excited state is O ₂ (A ³電子 u ⁺ ) or O ₂ (A ³ Σu ⁺ ). It is excited by O ₂ (B ³ Σu ⁻ ) and dissociates into oxygen atoms as shown in the following formulas.

O ₂ (X ³ Σg ⁻ ) + e → O ₂ (A ³ Σu ⁺ ) + e Equation (2-1) O ₂ (A ³ Σu ⁺ ) + e → O ( ³ P) + O ( ³ P) ) + E Formula (2-2) O ₂ (X ³ Σg ⁻ ) + e → O ₂ (B ³ Σu ⁻ ) + e Formula (2-3) O ₂ (B ³ Σu ⁻ ) + e → O ( ³ P) + O ( ¹ D) + e Equation (2-4)

Therefore, excited oxygen molecules and oxygen atoms are present in the oxygen plasma, and these become reactive species. When hydrogen H ₂ is introduced here, the following plasma is generated.

H ₂ + e → 2H Formula (3)

In the oxygen plasma, for example, the formula (2)
The oxygen plasma generated in -2) and the hydrogen plasma generated in equation (3) react to generate water vapor. Then, the surface of the heated semiconductor layer is oxidized by the water vapor, and an oxide film is formed on the surface of the semiconductor layer.

2H + O ( ³ P) → H ₂ O Formula (4)

In the manufacture of a semiconductor device, for example, the thickness of a silicon oxide film is optically measured based on ellipsometry. The problem of the prior art is caused by trying to form silicon oxide films having physically different thicknesses. However, in consideration of the actual operation of the semiconductor device, it is sufficient that the film thickness obtained from the capacitance of the insulating film by CV measurement, that is, the value required for the effective film thickness is not necessarily required. Does not need to satisfy the required value.

In the insulating film or the method of forming the same according to the present invention, the second region is made of a material having a relative dielectric constant ε ₂ different from the relative dielectric constant ε _{1 of} the material constituting the first region. I have. Assuming that the thickness (physical thickness) based on the physical measurement result of the second region is T ₂ , the effective thickness T ′ ₂ in terms of the oxide film of the second region can be expressed by the following equation. it can.

T ′ ₂ = T ₂ × (ε ₁ / ε ₂ )

In general, the relative dielectric constant ε ₁ of silicon oxide is about 4 and the relative dielectric constant ε ₂ of silicon oxide containing nitrogen atoms is about 6 to 9, although it depends on the manufacturing method and film forming conditions. Therefore,
When the physical thickness of the first region is equal to the physical thickness of the second region, the effective thickness T ′ ₂ of the second region is 0.44 to 0.67 of the physical thickness T ₁ of the _first region. Double.

Therefore, in the present invention, the conventional technology
Differently, the physical thickness T of the first region ₁And the thing in the second area
Physical thickness T_TwoNo need to vary, essentially insulation
Performing dry etching of the film and multiple thermal oxidation treatments
Becomes unnecessary.

When the plasma oxidation method and the plasma nitridation method are adopted, the first region and the second region are irradiated by irradiating a hydrogen gas, an oxygen gas, and a nitrogen-based gas with electromagnetic waves.
Can be formed, the formation of the insulating film can be essentially performed in one plasma processing apparatus, and the configuration of the apparatus for forming the insulating film can be simplified. In addition, if steam is generated by irradiating the hydrogen gas and the oxygen gas with electromagnetic waves, the steam is easily and reliably generated in a state where the oxidation rate is suppressed and controlled, that is, for example, even under reduced pressure. It is possible to form a thin oxide film by a humidifying oxidation method with the oxidation rate controlled. In addition, since the oxide film is formed by an oxidation method using water vapor, an oxide film having excellent time-dependent dielectric breakdown (TDDB) characteristics can be obtained.

[0044]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on embodiments with reference to the drawings.

(Embodiment 1) FIG. 1 shows a conceptual diagram of a single wafer processing apparatus suitable for carrying out the present invention. The plasma processing apparatus includes a processing chamber 10, a stage 11 on which a semiconductor layer (in the first embodiment, a silicon semiconductor substrate 20) is mounted, a magnet 13 provided outside the processing chamber 10,
Microwave waveguide 1 mounted on top of processing chamber 10
4 and a gas inlet 16 disposed at the top of the processing chamber 10.
A, 16B and 16C. Processing room 10
Is a plasma generation region 10A and a plasma processing region 10A.
B, and the stage 11 is disposed in the plasma processing region 10B. In addition, the silicon semiconductor substrate 2
A lamp as heating means 12 for heating 0 is housed in the stage 11. A magnetron 15 is attached to the microwave waveguide 14, and the microwaves of 1 GHz to 100 GHz (for example,
(A microwave of 2.45 GHz) is generated, and the microwave is transmitted through the microwave waveguide 14 to the processing chamber 10.
To the plasma generation region 10A. Further, the processing chamber 1 is supplied from each of the gas introduction sections 16A, 16B, and 16C.
A hydrogen gas, an oxygen gas, and a nitrogen gas are introduced into 0. In addition, an inert gas (for example, nitrogen gas) is introduced into the processing chamber 10 from a gas introduction unit 17 provided on a side surface of the processing chamber 10. Various gases introduced into the processing chamber 10 are exhausted out of the system from a gas exhaust unit 18 provided in a lower part of the processing chamber 10. Outside the processing chamber 10, a heater 19 for controlling the temperature inside the processing chamber 10 so as to prevent dew condensation inside the processing chamber 10 is provided.

In the plasma generation region 10A, water vapor is generated by irradiating an oxygen gas and a hydrogen gas with an electromagnetic wave of 1 GHz to 100 GHz (for example, a microwave of 2.45 GHz). Some of the water vapor is in a plasma state. In the plasma processing region 10B, the surface of the semiconductor layer is exposed to such water vapor, and the surface of the semiconductor layer is oxidized. Alternatively, in the plasma generation region 10A, nitrogen molecules in the excited state, nitrogen molecule ions generated by irradiating the nitrogen-based gas with an electromagnetic wave of 1 GHz to 100 GHz (for example, microwaves of 2.45 GHz),
The region where the second region is to be formed is nitrided by nitrogen atoms or nitrogen atom ions.

In Example 1, a silicon semiconductor substrate was used as the semiconductor layer. In the first embodiment,
The plasma oxidation method and the plasma nitridation method were adopted. A method for forming an insulating film using the plasma processing apparatus shown in FIG.
Hereinafter, description will be made with reference to FIGS. 2 and 3 which are schematic partial cross-sectional views of the silicon semiconductor substrate 20 and the like.

[Step-100] First, an N-type silicon wafer of 8 inches in diameter doped with phosphorus (prepared by CZ method)
LOC is formed on the silicon semiconductor substrate 20 by a known method.
An element isolation region 21 having an OS structure is formed, and then well ion implantation, channel stop ion implantation, and threshold adjustment ion implantation are performed. Note that the element isolation region 21 may have a trench structure, or may have a combination of a LOCOS structure and a trench structure. Thereafter, fine particles and metal impurities on the surface of the silicon semiconductor substrate 20 are removed by RCA cleaning, and then the surface of the silicon semiconductor substrate 20 is cleaned with a 0.1% aqueous hydrofluoric acid solution and pure water. Expose the surface. still,
Most of the surface of the silicon semiconductor substrate 20 is terminated with hydrogen, and a very small portion is terminated with fluorine.

[Step-110] Next, the silicon semiconductor substrate 20 is carried into the plasma processing apparatus shown in FIG. 1 from a door (not shown), and is placed on the stage 11, and then the inert gas ( For example, nitrogen gas) is introduced into the processing chamber 10. Then, the silicon semiconductor substrate 20 is heated to 800 ° C. by the heating means 12.

[Step-120] Then, the first region 22 is formed by oxidizing the surface of the semiconductor layer, and a second region formation region 23A where the second region 23 is to be formed is formed. . Specifically, an oxide film 24 is formed on the surface of the silicon semiconductor substrate 20 which is a semiconductor layer based on a plasma oxidation method. That is, the introduction of the inert gas (for example, nitrogen gas) as the dilution gas into the processing chamber 10 is interrupted, and the hydrogen gas and the oxygen gas are introduced into the processing chamber 10 from the gas introduction unit 16A and the gas introduction unit 16B. . At the same time, microwave power is supplied to the magnetron 15, and microwaves of 1 GHz to 100 GHz (for example, microwaves of 2.45 GHz) generated by the magnetron 15 are generated in the processing chamber 10 through the microwave waveguide 14. It is introduced into the area 10A. Thus, that is, by irradiating the hydrogen gas and the oxygen gas with the electromagnetic waves, the reactions of the above-described formulas (2-1) to (2-4) and the reactions of the formulas (3) and (4) occur. Water vapor is generated. The generated water vapor is applied to the plasma processing region 10 located below the processing chamber 10.
B, and the surface of the semiconductor layer (specifically, the silicon semiconductor substrate 20) heated by the heating means 12 is oxidized. Thus, the oxide film 2 having a thickness of 3.5 nm is formed on the surface of the semiconductor layer (specifically, the surface of the silicon semiconductor substrate 20).
4 ((A-1) and (A-1) in FIG. 2).
-2)). The conditions for forming the oxide film 24 are shown in Table 1 below.

[Table 1] Microwave power: 10 kW Microwave frequency: 2.45 GHz Oxygen gas flow rate: 10 SLM Hydrogen gas flow rate: 0.2 SLM Substrate temperature: 800 ° C.

[Step-130] Then, the first region 22
Is covered with a mask material 25. That is, the oxide film 24
Is completed, the supply of microwave power to the magnetron 15 and the introduction of hydrogen gas and oxygen gas into the processing chamber 10 are stopped, and an inert gas is introduced into the processing chamber 10 from the gas introduction unit 17. While cooling, the silicon semiconductor substrate 20 is cooled to room temperature, and then the silicon semiconductor substrate 20 is unloaded from the plasma processing apparatus. Then, a mask material made of a resist material is formed on the entire surface of the silicon semiconductor substrate 20 by a spin coating method, and the mask material on the second region formation planned region 23A is removed based on a known lithography technique, thereby forming the second region. The first region 22 is covered with a mask material 25 (see (B-1) and (B-2) in FIG. 2).

[Step-140] Next, the silicon semiconductor substrate 20 is again carried into the plasma processing apparatus shown in FIG. 1 from a door (not shown), and is placed on the stage 11, and then the nitrogen-based gas is introduced from the gas inlet 16C. Nitrogen gas (N ₂ gas)
Is introduced into the processing chamber 10. In addition, magnetron 15
To a microwave power of 1 GHz to 100 GHz generated by the magnetron 15 (for example,
2.45 GHz microwave) to the microwave waveguide 14.
Through the plasma generation region 10A of the processing chamber 10. Thus, that is, an excited state of a nitrogen molecule, a nitrogen molecule ion, a nitrogen atom or a nitrogen atom generated by the reaction of the above formulas (1-1) to (1-4) by irradiating a nitrogen-based gas with an electromagnetic wave. The ions reach the plasma processing region 10B located below the processing chamber 10, and only the surface of the second region formation planned region 23A is nitrided, and the second region 23 is formed.
Is formed (see (A-1) and (A-2) in FIG. 3). In FIG. 3, the nitrided portion of the insulating film 26 in the second region 23 is represented by reference numeral 26A.
Table 2 shows the conditions of the plasma nitriding treatment.
The reason for setting the temperature of the silicon semiconductor substrate 20 to room temperature is that nitrogen atoms are not
This is for suppressing diffusion into zero. Moreover, since the temperature of the silicon semiconductor substrate 20 is set to room temperature, it is possible to prevent the mask material 25 from being deteriorated.

[Table 2] Microwave power: 1 kW Microwave frequency: 2.45 GHz Nitrogen gas flow rate: 0.4 SLM Pressure: 0.16 Pa Substrate temperature: room temperature (25 ° C.)

As described above, by performing the plasma nitriding process, it is not necessary to perform the nitriding process at a high temperature unlike the thermal nitriding method. For example, the surface of the oxide film 24 can be nitrided at room temperature. The introduction of nitrogen atoms into the oxide film by the thermal nitridation method does not adversely affect the semiconductor device characteristics such as a decrease in current driving capability as a result of nitrogen entering the silicon semiconductor substrate 20. Furthermore, since nitrogen atoms are introduced into the insulating film, boron atoms contained in the gate electrode pass through the gate insulating film and reach the semiconductor layer by various heat treatments in the subsequent manufacturing steps of the semiconductor device. The problem that the threshold voltage of the PMOS semiconductor element fluctuates can be reliably avoided.

[Step-150] Thereafter, the mask material 25 is used.
Are removed by, for example, chemical cleaning using a mixture of sulfuric acid and hydrogen peroxide solution ((B-1) and (B-
2)).

Thus, the first region 22 and the second region 2
3, the insulating film 26 formed on the surface of the semiconductor layer (specifically, the surface of the silicon semiconductor substrate 20) can be obtained. The material forming the first region 22 is silicon oxide (SiO ₂ ), and the material forming the second region 23 is SiO _X N _Y / SiO ₂ . That is, the second region 23 is composed of material having a high dielectric constant epsilon ₂ than the dielectric constant epsilon ₁ having the first region 22. The insulating film 26 composed of the first region 22 has a memory (D
It functions as a gate insulating film for a transistor element constituting a RAM (RAM). On the other hand, the insulating film 26 including the second region 23 functions as a gate insulating film for a transistor element included in a logic circuit (ASIC). Although the physical thickness of the first region 22 and the second region 23 are substantially the same, the effective thickness T ′ ₂ of the second region 23 is the same as the physical thickness of the first region 22. It is thinner than T _1.

[Step-160] Thereafter, a semiconductor element may be manufactured by a known method. That is, the silicon semiconductor substrate 20 is carried into a known CVD apparatus. And p
A silicon layer (e.g., a polysilicon layer) that does not contain the impurity is formed by a CVD method. Next, the silicon layer is patterned based on a lithography technique and a dry etching technique. Then, a p impurity (for example, boron ion or BF ₂ ion) is implanted into the silicon layer and the silicon semiconductor substrate 20 by an ion implantation method. Thus, a gate electrode made of a silicon layer (specifically, a polysilicon layer) containing a p-type impurity can be formed on the first region 22 and the second region 23 constituting the insulating film 26. Thus, an LDD structure can be formed. Alternatively,
A silicon layer (for example, a polysilicon layer) containing a p-type impurity (for example, boron) is formed by a CVD method. Next, the silicon layer is patterned based on a lithography technique and a dry etching technique. Thus, a gate electrode made of a silicon layer (specifically, a polysilicon layer) containing a p-type impurity can be formed on the first region 22 and the second region 23 forming the insulating film 26. Thereafter, an LDD structure can be formed by implanting a p impurity (for example, boron ion or BF ₂ ion) into the silicon semiconductor substrate 20 by an ion implantation method. The gate electrode may have a two-layer structure (polycide structure) of a polysilicon layer and a metal silicide layer,
It may have a polymetal structure in which a polysilicon layer and a refractory metal layer (for example, a tungsten layer) are stacked.

Next, an insulating material layer is formed on the entire surface, and the insulating material layer is etched based on an anisotropic dry etching technique to form a sidewall on the side wall of the gate electrode.
Next, in order to form source / drain regions, impurities (for example, boron ions or B
After F ₂ ions are implanted by an ion implantation method, an activation heat treatment of the implanted impurities is performed. Thereafter, an interlayer insulating layer is formed on the entire surface by a CVD method, an opening is provided in the interlayer insulating layer above the source / drain region, and a wiring material layer is formed on the interlayer insulating layer including the inside of the opening by a sputtering method. Then, a wiring is formed by patterning a wiring material layer to obtain a PMOS semiconductor device.
Note that the NMOS semiconductor element can be manufactured by the same method except that impurities to be introduced are different.

(Embodiment 2) In recent years, the voltage of CMOS transistors has been reduced in order to reduce power consumption. Therefore, the CMOS transistors are sufficiently lower than the PMOS and NMOS semiconductor elements. Symmetric threshold voltages are required. To address such demands, PMO
In the S semiconductor element, instead of the conventional gate electrode composed of a polysilicon layer containing an n-type impurity, p
A gate electrode composed of a polysilicon layer containing a shaped impurity is used. Incidentally, the CMOSFET having such a structure is a CM having a dual gate structure.
It is called OSFET. However, boron atoms (B), which are commonly used p-type impurities, easily pass through the gate insulating film from the gate electrode to the silicon semiconductor substrate by various heat treatments in a semiconductor device manufacturing process after the formation of the gate electrode. , The threshold voltage of the PMOS semiconductor element is varied. Such a phenomenon becomes more conspicuous when the gate insulating film is made thinner to reduce the voltage.
By performing the nitriding treatment on the gate insulating film, it is possible to effectively avoid the occurrence of the boron atom penetration phenomenon.

The second embodiment is a modification of the first embodiment. In the second embodiment, after [Step-150], the insulating film 26 composed of the first region 22 and the second region 23 is formed in order to more effectively avoid the occurrence of the boron atom penetration phenomenon. On the other hand, a thermal nitriding treatment using NO gas is performed. Specifically, after cleaning the silicon semiconductor substrate 20 as necessary, it is carried into a resistance heating type thermal nitriding apparatus (not shown) in a nitrogen gas atmosphere at 700 ° C. After the temperature in the apparatus is stabilized, the ambient temperature in the thermal nitriding apparatus is raised to 900 ° C. Then, the atmosphere in the thermal nitriding apparatus is switched to the NO gas atmosphere, and the thermal nitriding is performed on the insulating film 26 for 5 minutes. Thereby, the insulating film 26 and the semiconductor layer (the silicon semiconductor substrate 20)
SiO _X N _Y is formed at the interface. More specifically, in the first region 22 SiO ₂ / SiO _X N _Y structure is formed, in the second region 23 SiO _X N _Y / SiO
_{A 2} / SiO _X N _Y structure is formed. This makes it possible to more effectively prevent the penetration of boron atoms. After the completion of the thermal nitridation treatment, the atmosphere in the thermal nitridation treatment apparatus was switched to a nitrogen gas atmosphere, and the temperature was increased to 700.
After the temperature is lowered to ゜ C, the silicon semiconductor substrate 20 is carried out of the thermal nitriding apparatus. Hereinafter, [Step-16] of Example 1
0].

Alternatively, after that, the silicon semiconductor substrate 20 is carried out of the thermal nitriding apparatus, and then the known CV
A semiconductor layer (specifically, a silicon semiconductor substrate 2)
0) is carried in. Then, a silicon layer containing no impurities (a polysilicon layer in the second embodiment) is formed on the entire surface by a CVD method. Then, based on a known lithography technique and an ion implantation technique, a p-channel type MOSFE is formed.
Boron to gate electrode for T, n-channel MOS
After phosphorus is respectively introduced into the gate electrode for the FET, the silicon layer is patterned. As a result, the p-type MOSFET for p-channel MOSFET is formed on the gate insulating film.
A gate electrode made of a silicon layer (specifically, a polysilicon layer) containing a shaped impurity can be formed. In addition, a gate electrode made of a silicon layer containing an n-type impurity (specifically, a polysilicon layer) for an n-channel MOSFET can be formed on the gate insulating film.
Thereafter, an LDD region is formed using a known technique, and then an insulating material layer is formed on the entire surface, and the insulating material layer is etched based on an anisotropic dry etching technique to form a sidewall on a side wall of the gate electrode. Form. Next, in order to form source / drain regions, a p-channel MOS is formed based on a known lithography technique and ion implantation technique.
After boron is introduced into the region of the silicon semiconductor substrate where the FET is to be formed and phosphorus is introduced into the region of the silicon semiconductor substrate where the n-channel MOSFET is to be formed, heat treatment for activating the implanted impurities is performed. Thereafter, an interlayer insulating layer is formed on the entire surface by a CVD method, an opening is provided in the interlayer insulating layer above the source / drain region, and a wiring material layer is formed on the interlayer insulating layer including the inside of the opening by a sputtering method. A p-type semiconductor element (more specifically, a p-channel MOSFET in a CMOSFET having a dual gate structure) can be obtained by forming and patterning a wiring material layer to form a wiring.

(Embodiment 3) Embodiment 3 is also a modification of Embodiment 1. In the first embodiment, the oxide film is formed by the plasma oxidation method while the silicon semiconductor substrate 20 is heated to 800 ° C., but in the third embodiment, two-stage oxidation is performed based on the plasma oxidation method. That is, the formation of the oxide film
After starting formation of an oxide film on the surface of the semiconductor layer at a temperature at which atoms mainly forming the semiconductor layer do not desorb from the surface of the semiconductor layer, the semiconductor layer is mainly formed from the surface of the semiconductor layer for a predetermined period. A first oxide film forming step of forming an oxide film while holding the semiconductor layer in a temperature range in which atoms do not desorb, and a temperature higher than a temperature range in which atoms mainly constituting the semiconductor layer do not desorb from the surface of the semiconductor layer; A second oxide film forming step of further forming an oxide film at a temperature until a desired thickness was obtained was constituted.
In the third embodiment, the plasma processing apparatus shown in FIG. 1 is used.

[Step-300] First, the same step as [Step-100] of the first embodiment is performed.

[Step-310] Next, the silicon semiconductor substrate 20 is carried into the plasma processing apparatus shown in FIG. 1 from a door (not shown), and is placed on the stage 11, and then the inert gas ( For example, nitrogen gas) is introduced into the processing chamber 10. Then, the silicon semiconductor substrate 20 is heated to 300 ° C. by the heating means 12. At this temperature, the Si—H bond on the surface of the semiconductor layer is not broken. Therefore, no irregularities (roughness) are generated on the surface of the semiconductor layer (the silicon semiconductor substrate 20 in the third embodiment).

[Step-320] Then, while introducing an inert gas (for example, nitrogen gas) as a diluting gas from the gas introduction unit 17 into the processing chamber 10, the gas is introduced from the gas introduction unit 16A and the gas introduction unit 16B into the processing chamber. Hydrogen gas and oxygen gas are introduced into 10. At the same time, microwave power is supplied to the magnetron 15 to generate 1 GH generated by the magnetron 15.
microwave of z to 100 GHz (for example, 2.45 G
(Microwave of 1 Hz) is introduced into the plasma generation region 10A of the processing chamber 10 through the microwave waveguide 14. Thereby, steam is generated. The generated steam is in processing chamber 1
0, reaches the plasma processing region 10B located below,
The surface of the semiconductor layer (specifically, the silicon semiconductor substrate 20) heated by the heating means 12 is oxidized. Thus, an oxide film (a silicon oxide film in Example 3) can be formed on the surface of the semiconductor layer. Table 3 below shows conditions for forming the oxide film. In this first oxide film forming step, an oxide film having a thickness of 1 nm is formed.

[Table 3] Microwave power: 10 kW Microwave frequency: 2.45 GHz Oxygen gas flow rate: 10 SLM Hydrogen gas flow rate: 0.2 SLM Inert gas flow rate: 10 SLM Substrate temperature: 300 ° C.

[Step-330] Then, the magnetron 1
The supply of the microwave power to the processing chamber 5 and the introduction of the hydrogen gas and the oxygen gas into the processing chamber 10 are interrupted, and the introduction of the inert gas from the gas inlet 17 into the processing chamber 10 is continued. The silicon semiconductor substrate 20 at 800 ° C.
Heat up to Since a thin oxide film is already formed on the surface of the semiconductor layer, no irregularities (roughness) are generated on the surface of the semiconductor layer (the silicon semiconductor substrate 20 in the third embodiment) in this temperature raising step. Next, hydrogen gas and oxygen gas are again introduced into the processing chamber 10 from the gas introduction unit 16A and the gas introduction unit 16B. At the same time, the microwave power is again supplied to the magnetron 15, and the microwave of 1 GHz to 100 GHz (for example, the microwave of 2.45 GHz) generated by the magnetron 15 is supplied to the processing chamber 10 through the microwave waveguide 14. It is introduced into the plasma generation region 10A. Thereby, steam is generated.
The generated water vapor reaches the plasma processing region 10B located below the processing chamber 10, and further oxidizes the surface of the semiconductor layer (specifically, the silicon semiconductor substrate 20) heated by the heating unit 12. Thus, an oxide film having a total thickness of 4 nm is formed on the surface of the semiconductor layer. Table 4 shows the conditions for forming the oxide film in the second oxide film forming step.

[Table 4] Microwave power: 10 kW Microwave frequency: 2.45 GHz Oxygen gas flow rate: 10 SLM Hydrogen gas flow rate: 0.2 SLM Inert gas flow rate: 10 SLM Substrate temperature: 800 ° C.

[Step-340] After that, [Step-130] to [Step-160] of the first embodiment are executed, or alternatively, of the first embodiment including the thermal nitriding treatment described in the second embodiment. By performing [Step-130] to [Step-160], a PMOS semiconductor element and an NMOS semiconductor element can be obtained.

(Embodiment 4) Embodiment 4 is also a modification of Embodiment 1. Embodiment 4 is different from Embodiment 1 in that after an oxide film is formed on the surface of the semiconductor layer, a heat treatment is performed on the formed oxide film. Hereinafter, a method for forming the insulating film according to the fourth embodiment will be described. In the fourth embodiment, the plasma processing apparatus shown in FIG. 1 is used.

[Step-400] [Step-10] of Example 1
0] to [Step-120], an oxide film having a thickness of 3.5 nm is formed on the surface of the semiconductor layer (the silicon semiconductor substrate 20 in the fourth embodiment).

[Step-410] Then, magnetron 1
The supply of the microwave power to the processing chamber 5 and the introduction of the hydrogen gas and the oxygen gas into the processing chamber 10 are stopped.
As a result, the temperature of the silicon semiconductor substrate 20 is raised to 850 ° C. Next, nitrogen gas containing 0.1% by volume of hydrogen chloride gas was introduced into the processing chamber 10 from the gas introduction unit 17,
Heat treatment for minutes. As a result, an oxide film having excellent time-zero dielectric breakdown (TZDB) characteristics and temporal dielectric breakdown (TDDB) characteristics can be obtained.

[Step-420] Thereafter, the gas introduction unit 17
The introduction of nitrogen gas containing 0.1% by volume of hydrogen chloride gas into the processing chamber 10 is stopped, and an inert gas (for example, nitrogen gas) is introduced into the processing chamber 10 from the gas introduction unit 17. Thereafter, by performing [Step-130] to [Step-160] of the first embodiment, or alternatively, [Step-130] to [Step-130] of the first embodiment including the thermal nitriding treatment described in the second embodiment.
By performing [Step-160], a PMOS semiconductor device or an NMOS semiconductor device can be obtained.
The heat treatment of the fourth embodiment may be added to the two-step gate insulating film forming process of the third embodiment.

(Embodiment 5) Embodiment 5 is also a modification of Embodiment 1. The fifth embodiment differs from the first embodiment in that a pyrogenic oxidation method is used for forming an oxide film.

FIG. 4 is a conceptual diagram of a vertical type oxide film forming apparatus for forming a silicon oxide film based on the pyrogenic oxidation method. This vertical type oxide film forming apparatus
Oxidizing furnace 30 of double tube structure made of quartz held vertically
(Corresponding to the processing chamber) and the wet gas and / or
A gas introduction unit 32 for introducing a gas, a gas exhaust unit 33 for exhausting a wet gas and / or gas from the oxidation furnace 30,
A heater 34 for maintaining the inside of the oxidizing furnace 30 at a predetermined atmospheric temperature through a cylindrical heat equalizing tube 36 made of iC, a substrate carrying-in / out part 40, and an inert gas such as nitrogen gas are introduced into the substrate carrying-in / out part 40. A gas inlet 41 for exhausting the gas, a gas exhaust unit 42 for exhausting gas from the substrate carrying-in / out unit 40, a shutter 35 separating the oxidizing furnace 30 and the substrate carrying-in / out unit 40,
An elevator mechanism 43 is provided for carrying the silicon semiconductor substrate 20 into and out of the oxidation furnace 30. A quartz boat 44 for mounting the silicon semiconductor substrate 20 is attached to the elevator mechanism 43. Further, the hydrogen gas supplied to the combustion chamber 50 is referred to as oxygen gas,
A wet gas is generated by mixing and burning at a high temperature in the furnace. The wet gas is introduced into the oxidation furnace 30 through the pipe 51, the gas flow path 31, and the gas introduction unit 32. The gas flow path 31 is provided in the oxidation furnace 30 having a double pipe structure.
Corresponds to the space between the inner wall and the outer wall.

An outline of a method for forming an oxide film based on a pyrogenic oxidation method using the vertical type oxide film forming apparatus shown in FIG. 4 will be described below.

[Step-500] First, the same step as [Step-100] in the first embodiment is performed.

[Step-510] Piping 52, combustion chamber 50,
Nitrogen gas is introduced into the oxidizing furnace 30 through the pipe 51, the gas flow path 31 and the gas introducing section 32, the inside of the oxidizing furnace 30 is set to a nitrogen gas atmosphere, and the heater 34 is heated by the heater 34 through the soaking tube 36. The ambient temperature is maintained at around 700 ° C. In this state, the shutter 35 is kept closed. The substrate loading / unloading section 40 is open to the atmosphere.
Then, the silicon semiconductor substrate 20 is loaded into the substrate loading / unloading section 40, and the silicon semiconductor substrate 20 is placed on the quartz boat 44. Silicon semiconductor substrate 20 to substrate carrying-in / out section 40
Is completed, the door (not shown) is closed, nitrogen gas is introduced into the substrate carrying-in / out section 40 from the gas introducing section 41, and the gas is exhausted from the gas exhausting section 42, and the inside of the substrate carrying-in / out section 40 is set to a nitrogen gas atmosphere.

[Step-520] When the inside of the substrate loading / unloading section 40 is sufficiently brought into the nitrogen gas atmosphere, the shutter 35 is opened and the elevator mechanism 43 is operated to activate the quartz boat 44.
Is raised, and the silicon semiconductor substrate 20 is carried into the oxidation furnace 30. When the elevator mechanism 43 reaches the highest position, the base of the quartz boat 44 stops communication between the oxidation furnace 30 and the substrate loading / unloading section 40.

[Step-530] Thereafter, the temperature of the oxidation furnace 30 in a nitrogen gas atmosphere is increased to 800 to 900 ° C. Then, the combustion chamber 50 is connected through the pipes 52 and 53.
An oxygen gas and a hydrogen gas are supplied into the inside, and the wet gas generated by mixing and burning the hydrogen gas and the oxygen gas at a high temperature in the combustion chamber 50 is supplied to a pipe 51, a gas passage 31, and a gas introduction unit 32. The gas is introduced into the oxidation furnace 30 through the gas exhaust unit 33 and exhausted from the gas exhaust unit 33. As a result, an oxide film is formed on the surface of the silicon semiconductor substrate 20. The combustion chamber 50
The internal temperature is increased by, for example, 700 heaters (not shown).
Keep at ~ 900 ° C.

[Step-540] After an oxide film having a desired thickness is formed, supply of oxygen gas and hydrogen gas into the combustion chamber 50 is stopped, and then inert gas such as nitrogen gas is supplied into the oxidation furnace 30. While introducing the gas, the ambient temperature of the oxidation
The temperature is lowered to about 0 ° C., then the elevator mechanism 43 is operated to lower the quartz boat 44, and then the silicon semiconductor substrate 20 is unloaded from the substrate loading / unloading section 40.

[Step-550] After that, [Step-130] to [Step-160] of the first embodiment are executed, or alternatively, the first embodiment including the thermal nitriding treatment described in the second embodiment is performed. By performing [Step-130] to [Step-160], a PMOS semiconductor element and an NMOS semiconductor element can be obtained. Further, based on the pyrogenic oxidation method of the fifth embodiment, the two-stage oxide film forming process described in the third embodiment may be executed, or the heat treatment described in the fourth embodiment may be applied. Good.

Although the present invention has been described with reference to the preferred embodiments, the present invention is not limited to these embodiments. The various conditions and the structures of the plasma processing apparatus and the oxide film forming apparatus described in the embodiments are merely examples, and can be appropriately changed. In some cases, for example, in the method of forming an insulating film described in Embodiment 1, [Step-120]
Subsequently, after only the surface of the oxide film 24 is nitrided by the plasma nitriding method, [Step-130] and thereafter may be executed.

Further, for example, [Step-33] of Example 3
0], the silicon semiconductor substrate 20 may be heated to 800 ° C. by the heating means 12 without stopping the supply of the microwave power to the magnetron 15 and the introduction of the hydrogen gas and the oxygen gas into the processing chamber 10. . In [Step-410] of the fourth embodiment, the temperature of the silicon semiconductor substrate 20 is increased by 8 by the heating unit 12 while introducing an inert gas (for example, nitrogen gas) from the gas introduction unit 17 into the processing chamber 10.
The temperature was raised to 50 ° C., but instead, for example, an inert gas (for example, nitrogen gas) containing 0.1% by volume of hydrogen chloride gas was introduced into the processing chamber 10 from the gas introduction unit 17 while the silicon semiconductor was The temperature of the substrate 20 may be raised to 850 ° C. by the heating means 12. Further, the atmosphere in each of the first oxide film forming step, the temperature raising step, and the second oxide film forming step may include, for example, a hydrogen chloride gas.

In the embodiment, the insulating film is formed exclusively on the surface of the silicon semiconductor substrate. However, according to the present invention, the insulating film can be formed on the epitaxial silicon layer formed on the substrate, It is also possible to form an insulating film on a polysilicon layer or an amorphous silicon layer formed on the insulating layer formed thereon. Alternatively, an insulating film may be formed on a silicon layer in the SOI structure. The formation of the oxide film and / or the nitridation of the oxide film can be performed not only in a single wafer process but also in a batch process in which a plurality of semiconductor layers are simultaneously processed.

After cleaning the surface of the semiconductor layer with a 0.1% aqueous solution of hydrofluoric acid and pure water in the examples, the semiconductor layer was treated with a plasma processing apparatus or an oxide film forming apparatus (hereinafter, these apparatuses are collectively referred to as these apparatuses). (Referred to as a plasma processing apparatus or the like), but the atmosphere from cleaning of the surface of the semiconductor layer to loading into the plasma processing apparatus or the like is changed to an inert gas (for example, nitrogen gas).
The atmosphere may be good. Note that such an atmosphere may be, for example, an atmosphere of a semiconductor layer surface cleaning apparatus set to an inert gas atmosphere, and a semiconductor layer (for example, a silicon semiconductor substrate) placed in a transport box filled with an inert gas. As shown in a schematic diagram in FIG. 5, a method for carrying in a plasma processing apparatus or the like, a surface cleaning apparatus, a plasma processing apparatus, or the like, a cluster tool apparatus including a transport path, a loader, and an unloader. The present invention can be achieved by a method in which the plasma processing apparatus and the like are connected by a transport path, and the atmosphere of the surface cleaning apparatus, the transport path, the plasma processing apparatus, and the like is an inert gas atmosphere.

Alternatively, instead of cleaning the surface of the semiconductor layer with a 0.1% hydrofluoric acid aqueous solution and pure water, a gas phase cleaning method using anhydrous hydrogen fluoride gas under the conditions shown in Table 5 is used. May be used to clean the surface of the semiconductor layer.
Note that methanol is added to prevent generation of particles. Alternatively, the surface of the semiconductor layer may be cleaned by a gas phase cleaning method using hydrogen chloride gas under the conditions shown in Table 6. Note that the atmosphere in the surface cleaning device or the atmosphere in the transfer path before the start of surface cleaning of the semiconductor layer or after completion of the surface cleaning may be an inert gas atmosphere,
For example, a vacuum atmosphere of about 1.3 × 10 ⁻¹ Pa (10 ⁻³ Torr) may be used. When the atmosphere in the transfer path or the like is a vacuum atmosphere, the atmosphere of the plasma processing apparatus or the like when the semiconductor layer is carried in is set to, for example, 1.3 × 10 ⁻¹ Pa (10 ^−3).
A vacuum atmosphere of about Torr may be set, and after the semiconductor layer is completely loaded, the atmosphere of the plasma processing apparatus or the like may be an inert gas (eg, nitrogen gas) atmosphere.

[Table 5] Anhydrous hydrogen fluoride gas: 300 SCCM Methanol vapor: 80 SCCM Nitrogen gas: 1000 SCCM Pressure: 0.3 Pa Temperature: 60 ° C

[Table 6] Hydrogen chloride gas / nitrogen gas: 1% by volume Temperature: 800 ° C

By employing these methods, it is possible to keep the surface of the semiconductor layer free from contamination or the like before the formation of the oxide film. It is possible to effectively prevent Si-OH from being taken in, thereby lowering the characteristics of the formed oxide film or generating a defective portion.

As described above, when the plasma oxidation method is employed, when forming an oxide film, hydrogen gas and oxygen gas are introduced into the processing chamber 10. In order to prevent a detonation reaction from being caused by flowing in and flowing out of the system, and to prevent a dry oxide film from being formed on the semiconductor layer, for example, [Step- 120], while introducing an inert gas (for example, nitrogen gas) as a diluting gas at a flow rate of 10 SLM from the gas introduction unit 17 into the processing chamber 10, the flow rate of the inert gas (eg, nitrogen gas) from the gas introduction unit 16 </ b> A into the processing chamber 10 is reduced to 0.1.
2 SLM of hydrogen gas is introduced, and then, for example, the introduction of oxygen gas at a flow rate of 10 SLM into the processing chamber 10 from, for example, the gas introduction unit 16B is started, and the inert gas processing chamber 1 for dilution
What is necessary is just to stop the introduction into 0. Next, microwave power is supplied to the magnetron 15, and the microwave of 2.45 GHz generated by the magnetron 15 is introduced into the plasma generation region 10 </ b> A of the processing chamber 10 through the microwave waveguide 14. By such an operation, the concentration of hydrogen gas in the processing chamber 10 before the generation of steam becomes a sufficiently low value, and it is possible to reliably prevent the detonation reaction from occurring, and furthermore, to surely form the dry oxide film. Can be prevented.

[0093]

According to the present invention, unlike the prior art, the physical thickness of the first region and the physical thickness of the second region are substantially the same (that is, the physical thickness is different). Without substantially changing the thickness), it is possible to form an insulating film composed of two regions having different effective thicknesses, and it is not necessary to perform dry etching of the oxide film or multiple thermal oxidation processes. Become. Therefore, it is possible to solve the problems in the conventional techniques such as etching damage and metal contamination occurring in, for example, a semiconductor layer region where a logic circuit is to be formed, and complicated control of an impurity profile for adjusting a threshold value.

If the plasma oxidation method and the plasma nitridation method are employed, the formation of the insulating film can be performed essentially in one plasma processing apparatus, and the structure of the apparatus for forming the insulating film can be simplified. And a thin oxide film can be formed by a humidification oxidation method with the oxidation rate being controlled.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a plasma processing apparatus suitable for performing a method of the present invention.

FIG. 2 is a schematic partial cross-sectional view of a silicon semiconductor substrate and the like for describing a method of forming an insulating film of Example 1.

FIG. 3 is a schematic partial cross-sectional view of the silicon semiconductor substrate and the like for explaining the method for forming the insulating film of the first embodiment, following FIG. 2;

FIG. 4 is a conceptual diagram of a vertical type oxide film forming apparatus for forming an oxide film based on a pyrogenic oxidation method.

FIG. 5 is a schematic view of a cluster tool device.

FIG. 6 is a schematic partial cross-sectional view of a silicon semiconductor substrate or the like for describing a conventional method of forming an insulating film composed of two regions having different thicknesses.

FIG. 7 is a schematic partial cross-sectional view of a silicon semiconductor substrate and the like for explaining a conventional method of forming an insulating film composed of two regions having different thicknesses, following FIG. 6;

[Explanation of symbols]

10 processing chamber, 10A plasma generation area, 1
0B: Plasma processing area, 11: Stage, 1
2 ... heating means, 13 ... magnet, 14 ... microwave waveguide, 15 ... magnetron, 16A, 16
B, 16C, 17: gas introduction unit, 18: gas exhaust unit, 19: heater, 20: silicon semiconductor substrate, 21: element isolation region, 22: first region ,
23 ... second region, 23A ... second region formation planned region, 24 ... oxide film, 25 ... mask material, 26
... Insulating film

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) H01L 27/108 21/8242 F-term (Reference) 5F045 AA09 AA20 AB03 AB32 AB34 AC03 AC11 AC13 AD04 AD07 AD12 AD13 AF03 CB10 DC63 DC69 EB13 EE12 HA15 HA22 5F048 AA07 AB01 AB03 AC01 AC03 BA01 BB06 BB07 BB11 BB12 BB16 BB17 BC06 BG12 DA20 DA21 5F058 BA20 BD01 BD04 BD10 BE03 BF29 BF30 BF63 BF73 BF74 BG01 JA08 NA08 JA08 PR21 PR22 PR44 PR54 ZA12

Claims (8)

[Claims] An insulating film formed on a surface of a semiconductor layer, wherein: (A) a first region; and (B) a dielectric constant different from a relative dielectric constant of a material constituting the first region. A second region composed of a substance having
An insulating film characterized by comprising: 2. The insulating film according to claim 1, wherein the material forming the first region is silicon oxide, and the material forming the second region is silicon oxide containing a nitrogen atom. 3. The insulating film according to claim 2, wherein the second region has substantially the same thickness as the first region. 4. The insulating film according to claim 2, wherein the second region is formed by nitriding silicon oxide. 5. The insulating film according to claim 4, wherein the second region is formed by irradiating silicon oxide with nitrogen plasma. 6. A semiconductor device having a first region and a second region formed on a surface of a semiconductor layer, wherein the second region has a relative dielectric constant different from a relative dielectric constant of a material constituting the first region. A method for forming an insulating film made of a material having the following characteristics: (a) oxidizing a surface of a semiconductor layer to form a first region and a second region where a second region is to be formed (B) covering the first region with a mask material; and (c) removing the mask material after subjecting the exposed second region to be formed to a nitriding treatment. And a method for forming an insulating film. 7. The insulating film according to claim 6, wherein the material forming the first region is silicon oxide, and the material forming the second region is silicon oxide containing nitrogen atoms. Forming method. 8. The method for forming an insulating film according to claim 6, wherein the nitriding treatment in the step (c) comprises irradiating a region to be formed with the second region with nitrogen plasma.